1. Field of the Invention
The disclosure relates generally to image recognition and distance calculation methods and devices, and, more particularly to methods and devices that automatically determine a height of at least one predefined scale, and determine a distance between a device, such as a digital level and a level ruler.
2. Description of the Related Art
In measurement instruments, levels can be used to measure height difference. A level, can use an optical device at its side, such as a telescope to view a level ruler positioned at the other side. Generally, a crisscross and two predefined scales respectively above and below of the crisscross are marked in the telescope, and an operator must manually view the positions of the crisscross and the predefined scales projected on the level ruler, and accordingly determine the height of the level ruler, and the distance between the level and the level ruler.
Currently, manual readings are required for most levels for related determinations. Since the determinations are performed manually, erroneous determinations frequently occur. To reduce erroneous determinations, some digital levels can provide automatic readings and determinations. However, the position of the level ruler, such as being upright, inverted or tilted, and the brightness of the location where the level ruler is positioned, may affect the determination results. Thus, the determination results of digital levels are often suspect to being inaccurate.